A. Field of Invention
This invention relates to an aquatic antifouling composition and a fishnet antifouling composition to be used for preventing ship-bottoms, other marine structures and fishnets such as nursery nets and stationary nets from being fouled or damaged by marine adhesive organisms.
B. Description of the Prior Art
Ships, specifically their bottoms and waterline zones, other marine structures and fishnets such as nursery nets and stationary nets are subject to adhesion and parasitism of various marine organisms: they include arthropods such as barnacles and goose barnacles, coelenterates such as hydras, annelids such as hydroides, tentacular animals such as Bugula neritina, mollusks such as mussels, and other collectively called animals; fine algae such as diatoms and blue-green algae, green algae such as flat green layers and see lettuces, brown algae such as Ceramium kondoi and Phaeophyceae, and others collectively called algae; and various kinds of bacteria called slime. Their adhesion affects the ships and so forth seriously. A great cost is required for removal of these livings and repairement or repainting of the ships, etc.
In the case of a ship, for example, a several percent increase in the resistance of its hull due to the adhesion of marine organisms causes a decrease in speed and a fall in the fuel efficiency, which would result in a serious loss.
Recently the advance of ocean development in the coastal regions has been encouraging construction and installation of large marine structures, structures, annexed thereto, and other similar structures. The structures exposed to sea water, for example, structures for harbor/facilities (such as nautical beacons, floating beacons, mooring buoys, floating piers, floating breakwaters, and floating docks), pipelines, bridges, tanks, water pipes in power stations, seaside industrial plants, mooring ships, mooring and floating fishing structures, fish preserving structures, and stationary nets and other facilities/structures for fishing, suffer various damage such as corrosion in the basal parts, sinking or loss due to the increased weight, loss of balance, etc. when the pollution-productive marine organisms have adhered and grown there.
In addition, at facilities, plants, and power stations located along seashores, when they use sea water for cooling or for the other purposes, the pollution-productive adhesive marine livings adhere to their seawater inlets and outlets, coastal structures such as channels and culverts, and growth there. The volume occupied by these livings sometimes reaches the order of some tens of percents of the inner volume of such tubular structures, which causes a decrease in the available cross-sectional area of waterways, an increase in the resistance to the liquid flow, choking of the screens to remove suspended solids, and and other damage.
Fishnets such as nursery nets and stationary nets and marine ropes are subject to adhesion of such marine organisms as barnacles, hydroides, ascidians, green algae and brown algae. Since their adhesion hinders the economic use of such nets and ropes, great labor and large expense are required for the maintenance of them.
Heretofore, for the protection of marine structures and facilities from the adhesion of harmful marine organisms sparingly soluble inorganic copper compounds, organic tin compounds, organic nitrogen-sulfur compounds and the like have been used.
These substances, however, have various drawbacks; some manifesting toxicity to men and beasts, others polluting environments, and yet others failing to maintain sufficient effect when used for a long time as an aquatic antifoulant. Organic tin compounds are highly effective in preventing the adhesion of marine organisms and they have been regarded as efficient antifouling components and widely used. Recently, however, drawbacks of these organic tin compounds--being sparingly degradable, accumulation in living bodies, toxicological problem against men and beasts, possibility to cause environmental pollution--have been drawing attention.
As antifouling components against marine organisms, tributyl tin methyacrylate copolymers, tributyl tin fluorides and other organic tin compounds are considered most desirable in terms of retention of efficacy and stability of effect. However, their safety to men and beasts, environmental pollution, etc. have become a big issue in the society.
In terms of safety to men and beasts and freedom from environmental pollution, metal salts of alkylenebisdithiocarbamic acid are rated as the most desirable antifouling components. In many cases, however, they are not satisfactory in terms of retention of efficacy and stability of effect. In order to solve these problems, a heavy metal salt of alkylenebisdithiocarbamic acid is combined with an inorganic copper compound to prepare an antifouling component, or some other antifouling components such as maleimide compounds are added to the said combination. But sufficient efficacy and stability have not yet been achieved.
Accordingly, the purpose of this invention is to provide an aquatic antifouling composition which is able to retain its effect for long periods, which is sparingly susceptible to physical or chemical deterioration when coated, which is highly safe to men and beasts, and at the same time which is least likely to cause environmental pollution.